The present invention relates to wrenches and more particularly to wrenches providing increased leverage for turning the handwheels of valves.
In certain industries and occupations it is sometimes necessary to open and close valves by means of a handwheel attached to the valve stem. When the valve is large and when the valve does not turn as freely as designed, the handwheel may not provide enough leverage to operate the valve. Various methods of aiding this process have been provided. U.S. Pat. No. 4,715,252 issued to A. Pella discloses a one-piece wrench that engages the outside of the rim and a spoke of the handwheel while force is applied by an extended handle. U.S. Pat. No. 2,086,722 issued to C. J. Matuella teaches a wrench with three projections to engage the rim. U.S. Pat. No. 2,539,262 issued to A. H. Moore describes a wrench whose two members alternately wrap under and over the wheel rim. U.S. Pat. No. 2,682,189 issued to W. K. Bergman teaches a similar device. U.S. Pat. No. 3,482,476 issued to M. M. Tanksley discloses a wrench with a first jaw movably connected to a second jaw in a sliding, translatory relationship urged together by a spring.
The prior art devices have not resolved certain problems. It is most important that the wrench grip tightly, especially when maximum force is applied to the handle, because that force is often applied by pulling the handle toward the user at face level. If the jaws lose their grip, the handle often smashes the face of the worker, often causing dental injuries.
The wrench must grip both large and small valves and work effectively in turning both clockwise and counterclockwise.